2 Seeking the Cause



Epidemiology is the study of the distribution of diseases in a population, and the application of this study to controlling outbreaks, epidemics and pandemics by understanding the origins and patterns of the spread of a disease. This module explores three major ideas in epidemiology:

  • identifying the first cases of an infectious disease,
  • determining the causative agent,
  • and tracking how it spread.

Below is a video students can watch in the "Student View" of this introduction that provides an epidemiological perspective on how the Ebola virus was discovered and its spread halted in a village.

The Story of Ebola

Students begin by learning how the first cases of Ebola and measles (Patient Zero or index case) were identified. Students then read about John Snow and the first recorded epidemiological investigation in which he determined the source of a cholera epidemic in 19th century London. Students then learn about the kinds of data modern day epidemiologists collect. They then apply their understandings to determining the cause of an outbreak of a respiratory disease in New Mexico. Students then return to Ebola and measles to determine the factors involved in the spread of these recent epidemics.

Learning outcomes

At the end of the module student should be able to:

  1. Describe methods for identifying “Patient Zero”
  2. Analyze data to identify the cause of an epidemic
  3. Explain the factors involved in the spread of Ebola and measles
  4. Apply their understandings about the factors involved in the spread of Ebola and measles to design an approach to stop the epidemics

Assumptions of Prior Knowledge

  • Students know the difference between infectious and noninfectious diseases
  • Students are familiar with viruses, bacteria, and parasites as agents of infectious diseases
  • Students are familiar with the meaning of the terms outbreak, epidemic and pandemic
  • Students can explain the meaning of emerging and reemerging diseases


Below are a list of materials for each activity in this module.

Activity 1: Causative Agent

  • One copy of epidemiological data, medical data, and laboratory data (per team)
  • One copy of Respiratory Distress Table (per team)
  • Poster board and markers (optional)

Activity 2: Tracking the Spread

  • One copy of Factors Chart for each student or each team